A worldwide meta-analysis (1977–2020) of sediment core dating using fallout radionuclides including <sup>137</sup>Cs and <sup>210</sup>Pb<sub>xs</sub>

Abstract

Abstract. Dating recent sediment archives (< 150 years) constitutes a prerequisite for environmental and climatic reconstructions. Radiocaesium (137Cs) emitted during thermonuclear bomb testing (∼ 1950–1980) and nuclear accidents and the decrease in excess lead-210 (210Pbxs) with depth are often combined to establish sediment core chronology. Although these methods have been widely used during the last several decades, there is a lack of structured and comprehensive worldwide synthesis of fallout radionuclide analyses used for dating sediment cores in environmental and Earth sciences. The current literature overview was based on the compilation of 573 articles published between 1977 and 2020, reporting the collection of 1351 individual dating sediment cores (the dataset can be accessed at https://doi.org/10.1594/PANGAEA.931493; Foucher et al., 2021). This review was conducted in order to map the locations where 137Cs fallout events were detected. These included the thermonuclear bomb testing peak in 1963, the Chernobyl accident in 1986, the Fukushima accident in 2011, and 24 additional events identified at 112 sites that led to local or regional radioactive releases (e.g., Sellafield accidents, Chinese nuclear tests). When 210Pbxs records were used along with 137Cs data, detailed information on the 210Pbxs age–depth models were also synthesized. With the current growing number of studies analyzing sediment cores and the increasing interest in the deployment of sediment fingerprinting techniques including radionuclides as potential discriminant properties, this spatialized synthesis provides a unique worldwide compilation for characterizing fallout radionuclide sources and levels at the global scale. This synthesis provides in particular a reference of 137Cs peak attribution for improving the sediment core dating, and it outlines the main questions that deserve attention in future research as well as the regions where additional 137Cs fallout investigations should be conducted in priority.

210Pbxs. is a viable alternative to 137Cs for tracing soil redistribution in mountain pastures affected by heterogeneous Chernobyl fallout

“…The value is high if compared to the fluxes expected for the latitudinal band of the considered site, which should range between 100 and 200 Bq m −2 yr −1 (Zhang et al, 2021), but it is in line with what has been observed at other mountain sites where FRN atmospheric deposition is fostered by orographic precipitation and scavenging (Le Roux et al, 2008). Despite being highly variable, also the 137 Cs reference inventory (9700 ± 2700 Bq m −2 ) is comparable with values determined in other mountain areas affected by the Chernobyl fallout (Alewell et al, 2014; Chawla et al, 2010), but exceeds the baseline inventory related to global fallout estimated for the considered latitudinal band (Foucher et al, 2021). Different patterns characterize 210 Pb xs.…”

“…In panel (e) MODERN 210 Pb xs. -derived rates are compared with results from the regression model at the sampling points [Color figure can be viewed at wileyonlinelibrary.com] also the 137 Cs reference inventory (9700 AE 2700 Bq m À2 ) is comparable with values determined in other mountain areas affected by the Chernobyl fallout(Alewell et al, 2014;Chawla et al, 2010), but exceeds the baseline inventory related to global fallout estimated for the considered latitudinal band(Foucher et al, 2021).Atmospheric flux210 Pbexc: ¼ Inventory Re f: site Á λ ð2Þ Different patterns characterize 210 Pb xs. and 137 Cs also when considering their distribution over depth (Figure 5a,b).…”

Drivers of 20th century sea‐level change in southern New Zealand determined from proxy and instrumental records

“…137 Cs concentrations, however, reach a clear peak at 0.065 m depth (Fig. 5b), which we attribute to 1965 ce , allowing 2 years for interhemispheric mixing and full atmospheric homogenization in the Southern Hemisphere (Hancock et al ., 2011; Gehrels et al ., 2012; Foucher et al ., 2021). Changes in the 206 Pb/ 207 Pb curve are less pronounced than at Pounawea (Gehrels et al ., 2008) or in Tasmania (Gehrels et al ., 2012); nevertheless, the 1890s onset of Southern Hemisphere pollution at 0.345 m depth and the introduction of unleaded petrol in the late 1980s are evident (Fig.…”

Foraminiferal Sea-Level Reconstructions From Major New Zealand Cities: Implications for Long-Term Vertical Land Movement Trends from Centennial Baselines

“…This interpretation assumes the pine plantation history for Pāuatahanui presented by Reilly (2013) is more accurate than the interpretations of Swales et al (2005), on the basis of the detailed local history presented by Reilly (2013) and aerial photography history presented by Retrolens (2021). This interpretation is supported by the peak in ¹³⁷Cs at 10.5 cm, depth (the 9.5 cm interval immediately above this was not sampled for ¹³⁷Cs) generally associated with 1963(Foucher et al, 2021, but this peak is not incorporated into the age model due to the visible redistribution of ¹³⁷Cs down-core to 19.5 cm depth. The 6.5 cm drop in Taraxacum spp.…”

“…In the Southern Hemisphere, the date of this peak is often treated as being delayed by 1 or 2 years to 1965 due to the time taken for the atmospheric concentrations to equilibrate (e.g. Gehrels et al, 2012;Foucher et al, 2021). At present, there is little agreement on whether the peak in New Zealand would represent 1963represent , 1964represent , or 1965represent (Foucher et al, 2021.…”